In order to work on an Arabic word, you need to create the object Lingua::AR::Word, passing the Arabic word encoded in utf8 to the constructor. You will then be able to get the stem through get_stem(). You will get the ArabTeX translittered form through get_arabtex().

Remember that input-output directly to shell will not be useful as long as your shell doesn't support utf8 encoded characters. In the example above, for example, I piped the output to another file forcing its writing in utf8.